fix(html): stop a cell spill at a covered cell, and advance the output pins

CHANGELOG.md

@@ -16,6 +16,9 @@ The release run heads these entries with the version and opens a fresh
 
 ## Unreleased
 
+- Spreadsheet text no longer spills over a cell that a merged cell from a row
+  above covers.
+
 - PDF annotations reject malformed indices, colors and geometry, and bound
   squiggle generation before writing output.
 

src/odr/internal/html/document_element.cpp

@@ -702,6 +702,9 @@ void html::translate_sheet(const Sheet &sheet, const WritingState &state) {
   const ElementRange shapes = sheet.shapes();
   const bool has_shapes = shapes.begin() != shapes.end();
 
+  // per column, the row where a cell spanning down from above ends
+  std::vector<std::uint32_t> span_end_row(end_column, 0);
+
   TableCursor cursor;
   for (std::uint32_t row_index = cursor.row(); row_index < end_row;
        row_index = cursor.row()) {
@@ -782,7 +785,9 @@ void html::translate_sheet(const Sheet &sheet, const WritingState &state) {
           const SheetCell cell_ahead = ahead == next_column && next.has_value()
                                            ? *next
                                            : sheet.cell(ahead, row_index);
-          if (!is_blank(cell_ahead)) {
+          // The merged cell from a row above paints over a covered position,
+          // which a reader may give as a blank cell.
+          if (span_end_row[ahead] > row_index || !is_blank(cell_ahead)) {
             bounded = true;
             break;
           }
@@ -887,6 +892,10 @@ void html::translate_sheet(const Sheet &sheet, const WritingState &state) {
       }
       state.out().write_element_end("td");
 
+      for (std::uint32_t column = column_index;
+           column < std::min(next_column, end_column); ++column) {
+        span_end_row[column] = row_index + cell_span.rows;
+      }
       cursor.add_cell(cell_span.columns, cell_span.rows);
       if (cursor.column() == next_column) {
         pending = next;

test/data.cmake

@@ -17,9 +17,9 @@ odr_test_data(
 odr_test_data(
         PATH "reference-output/odr-public"
         URL "https://github.com/opendocument-app/OpenDocument.test.output.git"
-        REVISION "429287e50942c53dd25afbc754217970c7499750")
+        REVISION "78e30814a59ef0c1409948628c6541da1449b027")
 
 odr_test_data(
         PATH "reference-output/odr-private"
         URL "https://github.com/opendocument-app/OpenDocument.test-private.output.git"
-        REVISION "9ade3a517a9787ffb2bcbb356e989b6d0cdbfd19")
+        REVISION "2e4e8efc8c2c3596280fa3bea57ebd7897e5cf66")

test/src/html_test.cpp

@@ -1631,6 +1631,24 @@ TEST(html, a_cell_spills_over_a_blank_neighbour_and_is_cut_by_a_full_one) {
   EXPECT_EQ(spills.find("nowrap;overflow:hidden"), std::string::npos);
 }
 
+// A covered cell shows the merged cell from the row above, so a spill stops
+// before it.
+TEST(html, a_cell_does_not_spill_into_a_merged_cell) {
+  const std::string page = render_sheet(
+      fods_file(fods_row(fods_blank() + fods_blank() +
+                         R"(<table:table-cell table:number-rows-spanned="2">)"
+                         R"(<text:p>merged</text:p></table:table-cell>)") +
+                    fods_row(fods_cell("one") + fods_blank() +
+                             "<table:covered-table-cell/>"),
+                fods_columns(3)),
+      HtmlConfig());
+
+  EXPECT_NE(page.find("max-width:0;white-space:nowrap;"
+                      "clip-path:inset(0 -96px 0 0)"),
+            std::string::npos);
+  EXPECT_EQ(page.find("clip-path:inset(0 -192px 0 0)"), std::string::npos);
+}
+
 // #822: and where nothing follows it at all, out onto the canvas — there is no
 // content to the right of the last column for it to paint over.
 TEST(html, a_cell_at_the_end_of_its_row_is_not_cut) {